Backup systems for solar water heaters are used (mainly in panels with more than 2 m2 of capture area) in high hot water demand systems or in processes where a constant hot water supply is necessary. Although there exist auxiliary water heating systems such as those cited in patents No. WO/2007/101899; WO/2007/053859; WO/2007/000112; WO/2005/061969; WO/2005/040695; WO/2005/026627; WO/2004/038305; WO/2002/084037; WO/1998/004874; WO/1996/018072; WO/1995/004905; WO/1982/003271; and WO/1981/002774, for solar water heaters with panels whose capture area is greater than 2 m2; normally traditional water heaters of low input power interconnected with the upper part of the storage tank of the solar panel are used as backup systems to prevent lack of hot water.
To satisfy demand with the greatest possible fuel economy, an electronic system was integrated with a gas electrovalve which gradually ignites the burner of the water heater, in a direct way by means of an electrical spark and a flame detector, such as the one cited in Patent No. WO/2007/057864. However, the water heater described in the aforementioned patent does not adapt itself fully to most hydraulic facilities, and therefore in many cases it is necessary to adapt or integrate other elements for its operation, increasing the equipment and maintenance cost of the entire system.